Behavioral inhibition/social reticence (BI/RET) is one of the most stable dispositional characteristics reported in childhood. Early BI/RET is often reinforced and exacerbated by children's reciprocal interactions with parents across development. Importantly, stable BI/RET places young children at subsequent risk for diagnosable anxiety disorders (namely, social phobia) during adolescence and adulthood and this risk is moderated by (a) overly directive/controlling parenting and (b) the child' lack of socal and emotion-regulation skills. The purpose of the proposed project is to conduct and evaluate a full-scale, randomized controlled trial during which we will randomly assign 150 45-60 month old children and their parents to either the Turtle Program (combined adapted Parent Child Interaction Therapy and Social Skills Facilitated Play (PCIT and SSFP) or to a less intensive, 6-session parent psychoeducation group, the best available treatment for preschool BI. The Turtle Program components highlight the development of skills to intervene in the reciprocal cycle of parent-child and peer interactions that contribute to the development of anxiety. Importantly, the group- based nature of SSFP provides a social context in which parents can practice behavioral skills with their child while being coached by the therapists. This trial will examine mediators an moderators of treatment response. Outcome measures (collected at pre-treatment, mid-treatment, post-treatment, and one-year follow-up) will include parent and teacher ratings/questionnaires of child anxiety symptoms/disorders, temperament, and social functioning; observational measures of parenting and children's social behaviors in the classroom; and heart rate physiology (a biological index of emotional reactivity and regulation).